The width \(\Gamma \)  in Eq. REF  is the width of a resonance measured in the RUS experiment, and is proportional to the energy dissipation that accompanies the vibrational mode associated with that resonance.[1]} Attenuation typically reaches a maximum when the timescale of the fluctuations match the frequency of the measured resonance. As the system approaches a phase transition, the relaxation time \(\tau \)  becomes very long (critical slowing down) and the condition \(\omega \tau = 1\)  can be satisfied for ultrasonic frequencies.
